Abrasion resistant, ductile steel

Abstract

The invention relates to the filed of powder metallurgy. A steel is disclosed, which is compacted from a powder mixture by means of pressure and heat, its microstructure arising mainly from two components, the first of which being austenitic (e.g., Hadfield manganese steel) and the second being an essentially martensitic component rich in hard precipitates. The austenitic microstructure is more ductile than the martensitic, and it effectively prevents the propagation of microscopic cracking. Thus, the material is suitable for use in wear parts subjected to strong forces, as in, e.g., stone crushers.

We claim: 
     
       1. Powder metallurgical abrasion resistant material produced by mixing with each other two or more different powder qualities and by compacting by means of pressure and temperature into a compact material, wherein at least one of the powder qualities is an iron based face centered cubic powder and another of the powder qualities is an iron based substantially martensitic powder, said second powder including at least 0.8 weight percent carbon and nitrogen altogether and at least 8 percent alloying elements forming precipitates of carbides, nitrides, carbonitrides or mixtures thereof, the alloying elements including chromium, molybdenum, titanium, niobium, tantalum, tungsten, vanadium and mixtures thereof. 
     
     
       2. A material in accordance with claim 1, wherein the face centered cubic powder is of Hadfield manganese steel having 0.5 to 1.8 weight percent C, 5 to 20 weight percent Mn, up to 10 weight percent precipitate-forming alloying elements including Cr, Mo, Ti, Ta, Nb, W, V and mixtures thereof, balance iron and residual impurities or an iron based powder including sufficient Ni, Mn and N, so as to produce an austenitic microstructure. 
     
     
       3. A material in accordance with claim 1, wherein the iron based, substantially martensitic powder includes a total of 1.8 to 3.6 weight percent carbon and nitrogen, 6 to 16 weight percent vanadium and up to 12 weight percent of other precipitate-forming alloying elements including chromium, molybdenum, titanium, niobium, tantalum, tungsten and mixtures thereof, the balance being iron and residual impurities. 
     
     
       4. A material in accordance with claim 1, wherein the volume percentage of the iron based, face centered cubic powder is from 15 to 70 percent. 
     
     
       5. A material in accordance with claim 1, wherein the percentage in volume of the iron based, face centered cubic powder is from 30 to 50 percent. 
     
     
       6. A material in accordance with claim 1, wherein the average particle size of any powder present in an amount greater than 15 % by volume is less than 1000 micrometers. 
     
     
       7. A material in accordance with claim 1, wherein the average particle size of the iron based, face centered cubic powder is smaller than the average particle size of the iron based, substantially martensitic, precipitate-containing powder. 
     
     
       8. A material in accordance with claim 1, wherein the compact material has been prepared using a completely uncompacted powder blend or using at least one powder blend partly or completely consolidated together such that a compound structure is formed after compaction of said materials. 
     
     
       9. A material in accordance with claim 1, wherein the compact material has been prepared using one or more powder blends and at least one homogeneous powder which is not blended with another powder, and such that a compound structure is formed after compaction. 
     
     
       10. A material in accordance with claim 1, wherein the compact material has been prepared by means of the simultaneous action of pressure and temperature. 
     
     
       11. A material in accordance with claim 1, wherein the temperatures used for compacting and heat treating the powder do not exceed 1250° C. 
     
     
       12. A material in accordance with claim 1, wherein the compact material comprises wear parts of stone crushers. 
     
     
       13. A material in accordance with claim 1, wherein the compact material comprises impact hammer crushers. 
     
     
       14. A material in accordance with claim 2, wherein the iron based, substantially martensitic powder includes a total of 1.8 to 3.6 weight percent carbon and nitrogen, 6 to 16 weight percent vanadium and up to 12 weight percent of other precipitate-forming alloying elements including chromium, molybdenum, titanium, niobium, tantalum, tungsten and mixtures thereof, the balance being iron and residual impurities. 
     
     
       15. A material in accordance with claim 2, wherein the volume percentage of the iron based, face centered cubic powder is from 15 to 70 percent. 
     
     
       16. A material in accordance with claim 3, wherein the volume percentage of the iron based, face centered cubic powder is from 15 to 70 percent. 
     
     
       17. A material in accordance with claim 14, wherein the volume percentage of the iron based, face centered cubic powder is from 15 to 70 percent. 
     
     
       18. A material in accordance with claim 2, wherein the percentage in volume of the iron based, face centered cubic powder is from 30 to 50 percent. 
     
     
       19. A material in accordance with claim 2, wherein the average particle size of any powder present in an amount greater than 15 % by volume is less than 1000 micrometers. 
     
     
       20. A material in accordance with claim 2, wherein the average particle size of the iron based, face centered cubic powder is smaller than the average particle size of the iron based, substantially martensitic, precipitate-containing powder.